1. Field of the Invention
The present invention is directed generally to systems and methods for monitoring retinal diseases, and more particularly to providing programs or video games for testing or mapping macular visual acuity.
2. Description of the Related Art
Age-related macular degeneration (AMD) is the leading cause of blindness in the United States and many other industrialized countries. AMD is a degeneration of the macula (central portion of the retina) that is associated with age. The progress of AMD is generally slow in the dry (nonexudative) form of the disease. However, in a portion of affected eyes, the wet (exudative) form of the disease can arise, where abnormal growth of new blood vessels and scar tissue under the retina can lead to rapid loss of vision. The abnormal growth of new blood vessels is called neovascularization, and therefore wet AMD is called neovascular AMD. Fortunately, neovascular AMD can now be treated by intravitreal injection of anti-angiogenic medications, which often stabilize and even reverse the loss of vision. However, early detection of neovascular AMD is needed for treatment to begin in a timely basis and to prevent the loss of vision.
The Amsler chart is a long-standing standard test for AMD that can detect distortions in vision caused by neovascular AMD. However, its sensitivity in detecting neovascular AMD is much lower than a newer test, which is called the preferential hyperacuity perimeter (PHP), wherein the Vernier acuity of the pericentral area is mapped. See Preferential Hyperacuity perimeter (PHP) Research Group. Results of a multicenter clinical trial to evaluate the preferential hyperacuity perimeter for detection of age-related macular degeneration. Retina 2005; 25:296-303. The PHP test is taught in U.S. Pat. No. 7,665,847 to Alster et al. Vernier acuity is defined by the resolution with which an eye can detect the relative location of two visual stimuli, such as the relative displacement of two line segments. Vernier acuity is also called “hyperacuity” because its threshold of perception is several times finer than the eye's ability to perceive spatial separation between features in a standard visual acuity target, such as the opening in the Landolt C, line separations in the Tumbling E, or standard optotypes. Compared to normal acuity, Vernier acuity is relatively unaffected by degradation of retinal image quality by cataract and other age-related conditions. Therefore, it is a good test to detect retinal abnormalities in an elderly population.
Currently, PHP testing is performed using a special device. Thus, the inventor has recognized a need for a test for macular visual acuity that may be run on commonly available computing devices with the limits of their available input and output facilities.